A device for determining an absolute angle of rotation of a rotational axis having a first measuring device for measuring an angle of rotation in a limited first measuring range and a second measuring device for determining an absolute angular range is known from DE 198 18 799 A1. The first measuring device includes two magnetic pole rings. The pole rings are arranged on the rotational axis and have north and south poles arranged circumferentially in alternating series. The rings have a different number of magnetic poles. A fixed magnetoresistive sensor is associated with each ring. Using this arrangement, it is indeed possible to determine an angle of rotation at a very high resolution, but only in a range from 0° to a maximum 180°. Therefore, DE 198 18 799 A1 proposes a second measuring device that has a Hall sensor and that, in contrast to the magnetoresistive sensors, makes it possible to determine the actual polarity of a measured magnetic pole. In this way, it is possible to expand the range of the absolute angle measurement to an interval ranging from 0° to 360°. However, to determine the absolute angle of rotation of a steering wheel, which can execute several rotations in both directions, this is still insufficient.
It is an object of the present invention to provide a device which is able to determine an absolute angle of rotation at a high resolution over a large measuring range.